Sinister foreign agents, led by the evil Kalinsky, utilize brutal torture, kidnapping and murder to execute their plan to create world conflict and chaos. Under the guise of "The Key Club" (the key that unlocks the door to peace), the group abducts Caldwell, the designer of a top-secret advanced design airplane capable of inflicting mass destruction. With national security threatened, Captain Hugh "Bulldog" Drummond begins to investigate. Alarmed by his snooping, the group sends their beautiful sharp-tongued cohort, Doris, to stop Drummond's interference. Romantic sparks fly and the situation threatens to explode as the ace detective trails the criminals to an isolated castle where the kidnapped scientist faces imminent execution.
Suave, dapper sleuth, "Bulldog" Drummond, is played by handsome leading man John Lodge for this Republic Picture. Lodge joined a line-up of other notable character actors of the era, including Ray Milland, Ralph Richardson and Ronald Colman (who also took on the role in early film adaptations).